High-efficiency data center cooling

ABSTRACT

High-efficiency cooling is performed in a data center in response to a cooling and/or humidity demand using a system having multiple cooling loops. The system includes a plurality of integrated cooling systems each comprising one or more specifically sized chillers and a liquid loop to address the cooling demand. A free cooling heat exchanger is coupled to the first liquid loop for use when a wet-bulb temperature surrounding the data center is at or below a free cooling set point of the first chilled liquid loop. The system isolates humidity control components to a second chilled liquid loop, and enables greater control of the first chilled liquid loop of the data center to meet specific IT loads.

The present patent document is a divisional of U.S. patent applicationSer. No. 13/591,753, filed Aug. 22, 2012, entitled “HIGH-EFFICIENCY DATACENTER COOLING”, the disclosure of which is incorporated herein byreference.

BACKGROUND Technical Field

This invention relates generally to managing energy in a data center,and more specifically, to high-efficiency data center cooling using aplurality of cooling systems.

Related Art

Traditional data centers conventionally include a plurality ofindividual computing resources contained within a housing structure.Data centers, or other physical spaces, benefit from an adequate andoptimized power and cooling infrastructure. Maintaining data centers atdesired temperatures (e.g., set points) helps prevent computer hardware(e.g., IT infrastructure) from overheating and malfunctioning. To thisend, many data centers are cooled to relatively low temperatures (e.g.,75° F.) to increase equipment reliability and useful life, and to avoiddowntime for repair and/or replacement.

As data centers consume more and more electricity, and Chief InformationOfficer (CIO) budgets remain relatively fixed, extreme pressure has beenmounting to make data centers more energy efficient. Data centers arebecoming more virtualized, leading to higher and more unpredictablecooling requirements, making energy efficiency more challenging. Inresponse, standards organizations like the American Society of HeatingRefrigeration and Air conditioning Engineers (ASHRAE) and the EuropeanUnion Code of Conduct for Datacenters, have adopted more relaxedenvironmental standards for data centers, thus allowing for higherserver inlet temperatures. Higher server inlet conditions encourage newand innovative design and control concepts that are unique to the datacenter space. Unlike other types of building environments, data centershave extremely low latent loads because IT load contributes onlysensible heat, as there are very few human beings in the space to addhumidity to the data center air, and fresh air make up is very low.

It is possible to design the infrastructure that supports the datacenter with variable speed devices and options for free cooling whenoutside environmental conditions are favorable. While these methods mayresult in measurable energy savings, they do not fully maximize varyingenvironmental conditions for increased savings.

SUMMARY

In general, embodiments of the invention provide approaches forhigh-efficiency cooling in a data center in response to a cooling and/orhumidity demand using a data center cooling system having multiplecooling loops to allow for a higher chilled liquid temperature of afirst chilled liquid loop, while maintaining data center roomtemperature and humidity control. Specifically, the data center coolingsystem includes a plurality of integrated cooling systems eachcomprising one or more specifically sized chillers and a liquid loop toaddress the cooling demand. A free cooling heat exchanger is coupled tothe first liquid loop for use when a wet-bulb temperature surroundingthe data center is capable of producing a condenser water that is at adifferential temperature below a return temperature of the first chilledliquid loop. The data center cooling system isolates humidity controlcomponents to a second chilled liquid loop, and enables greater controlof the first chilled liquid loop of the data center to meet specific ITloads, thereby maximizing energy savings during both normal and freecooling operation.

One aspect of the present invention includes a data center coolingsystem comprising: a first cooling system operable to maintain apredetermined set point of a first liquid loop to address a coolingdemand within the data center, the first cooling system comprising achiller; a second cooling system operable to maintain a pre-determinedset point of a second liquid loop to address the humidity and coolingdemand within the data center, the second cooling system comprising oneor more chillers sized to have a capacity lesser than that of thechiller of the first liquid loop, and wherein the predetermined setpoint of the first liquid loop is higher than the predetermined setpoint of the second liquid loop; a heat exchanger coupled to the firstliquid loop for use when a wet-bulb temperature surrounding the datacenter is below a pre defined set point the heat exchanger configured tooperate in parallel or in series with the chiller of the first liquidloop; and a flow control device coupling the first cooling system withthe second cooling system.

Another aspect of the present invention provides a data center coolingsystem comprising: a memory medium comprising instructions; a buscoupled to the memory medium; and a processor coupled to a controllervia the bus that when executing the instructions causes the system to:analyze an environmental condition of the data center; activate a heatexchanger in response to the environmental condition to maintain apredetermined set point for a first liquid loop of a first coolingsystem in the case that an outside wet-bulb temperature surrounding thedata center is below a free cooling set point; activate a chiller of asecond cooling system to address the environmental condition in the caseof either of the following: the outside ambient temperature surroundingthe data center is at a preset differential above the free cooling setpoint, and the free cooling heat exchanger is unable to maintain thepredetermined set point for the first cooling system; operate a flowcontrol device to maintain the predetermined set point for a liquid loopof the first cooling system; and activate a chiller of the first coolingsystem to address the environmental condition in the case that theactivation of the chiller of the second cooling system is unable tomaintain the predetermined set point for the first liquid loop.

Another aspect of the present invention provides a computer-readablestorage medium storing computer instructions, which, when executed,enables a computer system to provide data center cooling, the computerinstructions comprising: analyzing an environmental condition of thedata center; activating a heat exchanger in response to theenvironmental condition to maintain a predetermined set point for afirst liquid loop of a first cooling system in the case that an outsidewet-bulb temperature surrounding the data center is below a free coolingset point; activating a chiller of a second cooling system to addressthe environmental condition in the case of either of the following: theoutside ambient temperature surrounding the data center is above thefree cooling set point, and the free cooling heat exchanger is unable tomaintain the predetermined set point for the first cooling system;operating a flow control device to maintain the predetermined set pointfor a liquid loop of the first cooling system; and activating a chillerof the first cooling system to address the environmental condition inthe case that the activation of the chiller of the second cooling systemis unable to maintain the predetermined set point for the first liquidloop.

Another aspect of the present invention provides a method for datacenter cooling, the method comprising: analyzing, by a controller, anenvironmental condition of the data center; activating, by thecontroller, a heat exchanger in response to the environmental conditionto maintain a predetermined set point for a first liquid loop of a firstcooling system in the case that an outside wet-bulb temperaturesurrounding the data center is below a free cooling set point;activating, by the controller, a chiller of a second cooling system toaddress the environmental condition in the case of either of thefollowing: the outside ambient temperature surrounding the data centeris above the free cooling set point, and the free cooling heat exchangeris unable to maintain the predetermined set point for the first coolingsystem; operating, by the controller, a flow control device to maintainthe predetermined set point for a liquid loop of the first coolingsystem; and activating, by the controller, a chiller of the firstcooling system to address the environmental condition in the case thatthe activation of the chiller of the second cooling system is unable tomaintain the predetermined set point for the first liquid loop.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the invention will be more readilyunderstood from the following detailed description of the variousaspects of the invention taken in conjunction with the accompanyingdrawings in which:

FIG. 1 shows a schematic depiction of an exemplary computing environmentfor enabling data center cooling according to illustrative embodiments;

FIG. 2 shows a schematic depiction of a data center cooling systemaccording to illustrative embodiments; and

FIG. 3 shows a process flow for data center cooling according toillustrative embodiments.

The drawings are not necessarily to scale. The drawings are merelyrepresentations, not intended to portray specific parameters of theinvention. The drawings are intended to depict only typical embodimentsof the invention, and therefore should not be considered as limiting inscope. In the drawings, like numbering represents like elements.

DETAILED DESCRIPTION

Exemplary embodiments now will be described more fully herein withreference to the accompanying drawings, in which exemplary embodimentsare shown. Embodiments of the invention provide approaches forhigh-efficiency cooling in a data center in response to a cooling and/orhumidity demand using a data center cooling system having multiplecooling loops to allow for a higher chilled liquid temperature of afirst chilled liquid loop, while maintaining data center roomtemperature and humidity control. Specifically, the data center coolingsystem includes a plurality of integrated cooling systems eachcomprising one or more specifically sized chillers and a liquid loop toaddress the cooling demand. A free cooling heat exchanger is coupled tothe first liquid loop for use when a wet-bulb temperature surroundingthe data center is below a differential of the return temperature (at orbelow a free cooling set point) of the first chilled liquid loop. Thedata center cooling system isolates humidity control components to asecond chilled liquid loop, and enables greater control of the firstchilled liquid loop of the data center to meet specific IT loads,thereby maximizing energy savings during both normal and free coolingoperation.

It will be appreciated that this disclosure may be embodied in manydifferent forms and should not be construed as limited to the exemplaryembodiments set forth herein. Rather, these exemplary embodiments areprovided so that this disclosure will be thorough and complete and willfully convey the scope of this disclosure to those skilled in the art.The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of this disclosure.For example, as used herein, the singular forms “a”, “an”, and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. Furthermore, the use of the terms “a”, “an”, etc.,do not denote a limitation of quantity, but rather denote the presenceof at least one of the referenced items. It will be further understoodthat the terms “comprises” and/or “comprising”, or “includes” and/or“including”, when used in this specification, specify the presence ofstated features, regions, integers, steps, operations, elements, and/orcomponents, but do not preclude the presence or addition of one or moreother features, regions, integers, steps, operations, elements,components, and/or groups thereof.

Reference throughout this specification to “one embodiment,” “anembodiment,” “embodiments,” or similar language means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the presentinvention. Thus, appearances of the phrases “in one embodiment,” “in anembodiment,” “in embodiments” and similar language throughout thisspecification may, but do not necessarily, all refer to the sameembodiment.

With reference now to the figures, FIG. 1 depicts a system 100 thatfacilitates data center cooling in response to an environmentalcondition (e.g., a cooling and/or humidity demand). As shown, system 100includes computer system 102 deployed within a computer infrastructure104. This is intended to demonstrate, among other things, thatembodiments can be implemented within a network environment 106 (e.g.,the Internet, a wide area network (WAN), a local area network (LAN), avirtual private network (VPN), etc.), a cloud-computing environment, oron a stand-alone computer system. Still yet, computer infrastructure 104is intended to demonstrate that some or all of the components of system100 could be deployed, managed, serviced, etc., by a service providerwho offers to implement, deploy, and/or perform the functions of thepresent invention for others.

Computer system 102 is intended to represent any type of computer systemthat may be implemented in deploying/realizing the teachings recitedherein. In this particular example, computer system 102 represents anillustrative system for providing data center cooling. It should beunderstood that any other computers implemented under variousembodiments may have different components/software, but will performsimilar functions. As shown, computer system 102 includes a processingunit 108 capable of operating with a controller 110 stored in a memoryunit 112 to provide data center cooling, as will be described in furtherdetail below. Also shown is a bus 113, and device interfaces 115.

Processing unit 108 refers, generally, to any apparatus that performslogic operations, computational tasks, control functions, etc. Aprocessor may include one or more subsystems, components, and/or otherprocessors. A processor will typically include various logic componentsthat operate using a clock signal to latch data, advance logic states,synchronize computations and logic operations, and/or provide othertiming functions. During operation, processing unit 108 receives signalstransmitted over a LAN and/or a WAN (e.g., T1, T3, 56 kb, X.25),broadband connections (ISDN, Frame Relay, ATM), wireless links (802.11,Bluetooth, etc.), and so on. In some embodiments, the signals may beencrypted using, for example, trusted key-pair encryption. Differentsystems may transmit information using different communication pathways,such as Ethernet or wireless networks, direct serial or parallelconnections, USB, Firewire®, Bluetooth®, or other proprietaryinterfaces. (Firewire is a registered trademark of Apple Computer, Inc.Bluetooth is a registered trademark of Bluetooth Special Interest Group(SIG)).

In general, processing unit 108 executes computer program code, such asprogram code for operating controller 110, which is stored in memoryunit 112 and/or storage system 114. While executing computer programcode, processing unit 108 can read and/or write data to/from memory unit112 and storage system 114. Storage system 114 may comprise VCRs, DVRs,RAID arrays, USB hard drives, optical disk recorders, flash storagedevices, and/or any other data processing and storage elements forstoring and/or processing data. Although not shown, computer system 102could also include I/O interfaces that communicate with one or morehardware components of computer infrastructure 104 that enable a user tointeract with computer system 102 (e.g., a keyboard, a display, camera,etc.).

Referring now to FIG. 2 , the structure and operation of a data centercooling system 120 will be described in greater detail. As shown, datacenter cooling system 120 includes a first (i.e., primary) coolingsystem 122 operable to maintain a predetermined set point of a firstliquid (e.g., water) loop 124 to address a cooling and humidity demandwithin a data center 126, the cooling demand caused by an increasedtemperature resulting from an IT load, for example. Data center coolingsystem 120 further comprises a second (i.e., secondary) cooling system132 operable to maintain a pre-determined set point of a second liquid(e.g., water) loop 134 to address the cooling demand within data center126. In exemplary embodiments, the predetermined set point of firstliquid loop 124 is maintained higher than the predetermined set point ofsecond liquid loop 134. In one non-limiting example, the set pointtemperature of second liquid loop 134 is approximately 40-50° F., whilethe set point temperature of first liquid loop 124 is approximately55-65° F. entering data center 126 and approximately 65-75° F. exitingdata center 126. As will be described in further detail below,integration of first liquid loop 124 and second liquid loop 134according to exemplary embodiments allows for a higher chilled liquidtemperature of first liquid loop 124, thereby maximizing energyefficiency within data center 126 during both normal and free coolingoperation.

As shown, data center cooling system 120 further includes one or morechillers 138 operable with first liquid loop 124, and one or morechillers 140 operable with second liquid loop 134, wherein chiller 140of second liquid loop 134 is purposely sized to have a lesser capacity(i.e., heat transfer capacity (enthalpy difference) and rate of flow ofliquid coolant) than chiller 138 of first liquid loop 124. In onenon-limiting embodiment, chiller 140 of second liquid loop 134 has acapacity of approximately 20-30% of the capacity of chiller 138 of firstliquid loop 124.

Data center cooling system 120 further includes one or more heatexchangers 144 coupled to first liquid loop 124 for use when an ambienttemperature surrounding data center 126 is below a pre-defined setpoint. Specifically, heat exchanger 144 is configured to maintain theset point of first liquid loop 124 during free cooling operation of datacenter cooling system 120. That is, during cooler weather conditions,the outside ambient temperature can help save energy in data centercooling system 120. Free cooling can be used to save energy bymaintaining chiller 138 of first liquid loop 124 in an ‘off’ state for alonger period of time whenever the outside wet-bulb temperature dropsbelow the required set point (i.e., a differential with the returntemperature of first liquid loop 124). In one non-limiting embodiment,first liquid loop 124 contributes to an increase of approximately 50%more free cooling hours for data center 120 before returning to normaloperation. As shown, heat exchanger 144 operates in parallel or inseries with chiller 138 of first liquid loop 124.

Data center cooling system 120 further includes a plurality of pumps148A-C, and a flow control device (e.g., a three-way valve) 150 couplingfirst liquid loop 124 of first cooling system 122 with second liquidloop 134 of second cooling system 132. As will be described in furtherdetail below, in response to a cooling demand during operation, one ormore pumps 148A-C are activated, and flow control device 150 opens(e.g., from first liquid loop 124 to second liquid loop 134) to maintainthe set point of first liquid loop 124. This intermixing of liquidbetween the two liquid loops lowers the temperature of first liquid loop124, thus preventing, or at least delaying, the starting of chiller 138of first cooling system 122.

Data center 126 further includes a plurality of sensors 130 forcapturing data representing attributes of the environment surroundingand within data center 126 including, but not limited to: temperature,humidity, airflow, carbon emissions, etc. Sensors 130 can include anytype of sensor capable of capturing environmental conditions of datacenter 126. Data center 126 collects and routes signals representingoutputs from sensors 130 to controller 110. The signals can betransmitted over a LAN and/or a WAN (e.g., T1, T3, 56 kb, X.25),broadband connections (ISDN, Frame Relay, ATM), wireless links (802.11,Bluetooth, etc.), and so on. Different sensor systems may transmitinformation using different communication pathways, such as Ethernet orwireless networks, direct serial or parallel connections, USB,Firewire®, Bluetooth®, or other proprietary interfaces. (Firewire is aregistered trademark of Apple Computer, Inc. Bluetooth is a registeredtrademark of Bluetooth Special Interest Group (SIG)). In someembodiments, sensors 130 are capable of two-way communication, and thuscan receive signals (to power up, to sound an alert, etc.) fromcontroller 110.

Data center cooling system 120 further includes a HVAC unit 152 operablewith second cooling system 132 for maintaining a dew point of datacenter 126. More specifically, HVAC unit 152 operates with controller110 and chiller 140 to control humidity in data center 126 using dewpoint control in HVAC unit 152. In one embodiment, HVAC unit 152provides humidity control support to cooling system 132, which may beactivated in response to a humidity demand in data center 120.

It should be understood that HVAC unit 152 may include ductwork,multiple air supply vents and diffusers (not shown). Additionally, itshould be understood that the HVAC ductwork, multiple air supply ventsand diffusers can be in the ceiling of data center 126, the walls ofdata center 126 (e.g., at different elevations on the walls) and/or thefloors of data center 126 (e.g., within a sub floor wiring layer). Asshown, HVAC unit 152 is coupled to second liquid loop 134, and isallowed limited direct operation with first cooling system 122 due tothe decreased dehumidification need within data center 126.

In one embodiment, second cooling system 132 includes a set of thermalenergy storage (TES) units 158 coupled to second liquid loop 134 fortemporary storage of thermal energy. TES units 158 improve energyperformance by smoothing energy supply and increasing reliability. Inone non-limiting example, chiller 140 works in conjunction with TESunits 158 during peak daytime hours to manage the cooling load. Duringoff-peak hours, chiller 140 charges TES units 158 for use during futurecooling, e.g., in case of power failure.

Referring now to FIGS. 2-3 , an exemplary control sequence 200 forproviding data center cooling will be described in greater detail. Inthis embodiment, exemplary control sequence 200 considers both normaland free cooling operation. As shown, control sequence 200 begins, andat 201, a cooling demand (e.g., a temperature increase from an IT load)received from the sensors 130 of the data center 126 is analyzed. At202, the outside ambient wet and dry temperature surrounding the datacenter is analyzed. At 203, it is determined whether the outside ambienttemperature surrounding data center 126 is above or below a free coolingset point. If the ambient temperature is below the free cooling setpoint, data center cooling system 120 operates in a free cooling mode,and heat exchanger 144 is activated at 204. Heat exchanger 144 continuesto operate, and at 205, it is determined whether the set point of firstliquid loop 124 and/or second liquid loop 134 can be maintained by heatexchanger 144 alone. If no, heat exchanger 144 continues to operate, andchiller 140 of second cooling system 132 is activated. Alternatively, asdetermined at 203, chiller 138 and/or chiller 140 is activated inresponse to the cooling demand and/or the humidity demand, and operateswithout heat exchanger 144 in the case that the outside ambienttemperature surrounding data center 126 is above the free cooling setpoint.

Next, at 207, flow control device 150 opens from first liquid loop 124to second liquid loop 134 to provide intermixing thereof to lower theset point of first liquid loop 124. At 208, it is determined whether theset point of first liquid loop 124 is maintained. If yes, chiller 140 ofsecond liquid loop 134 remains operational to provide cooling to datacenter 126. However, if the set point is not being maintained, i.e.,chiller 140 is operating at a maximum load, flow control device 150 isclosed and chiller 138 of first liquid loop 124 is activated at 209 tomaintain the set point of first liquid loop 124. At this point, chiller138 will have enough load to run at higher efficiency. Next, at 210, itis determined if the load on data center 126 has decreased a determinedamount (e.g., 25-30%) and is therefore no longer operating asefficiently. If no, control sequence 200 returns to 209 and chiller 138of first liquid loop 124 remains operational. If yes, chiller 138 offirst liquid loop 134 is shut down, and cooling demand is again analyzedat 201.

It can be appreciated that the approaches disclosed herein can be usedwithin a computer system to provide high-efficiency data center cooling.In this case, controller 110 can be provided, and one or more systemsfor performing the processes described in the invention can be obtainedand deployed to computer infrastructure 104. To this extent, thedeployment can comprise one or more of (1) installing program code on acomputing device, such as a computer system, from a computer-readablestorage medium; (2) adding one or more computing devices to theinfrastructure; and (3) incorporating and/or modifying one or moreexisting systems of the infrastructure to enable the infrastructure toperform the process actions of the invention.

The exemplary computer system 102 (FIG. 1 ) may be described in thegeneral context of computer-executable instructions, such as programmodules, being executed by a computer. Generally, program modulesinclude routines, programs, components, logic, data structures, and soon, that perform particular tasks or implement particular abstract datatypes. Exemplary computer system 102 may be practiced in distributedcomputing environments where tasks are performed by remote processingdevices that are linked through a communications network. In adistributed computing environment, program modules may be located inboth local and remote computer storage media including memory storagedevices.

Computer system 102 carries out the methodologies disclosed herein. Forexample, the flowchart of FIG. 3 illustrates the architecture,functionality, and operation of possible implementations of systems,methods, and computer program products according to various embodimentsof the present invention. In this regard, each block in the flowchartmay represent a module, segment, or portion of code, which comprises oneor more executable instructions for implementing the specified logicalfunction(s). It should also be noted that, in some alternativeimplementations, the functions noted in the blocks might occur out ofthe order depicted in the figures. For example, two blocks shown insuccession may, in fact, be executed substantially concurrently. It willalso be noted that each block of flowchart illustration can beimplemented by special purpose hardware-based systems that perform thespecified functions or acts, or combinations of special purpose hardwareand computer instructions.

Some of the functional components described in this specification havebeen labeled as systems or units in order to more particularly emphasizetheir implementation independence. For example, a system or unit may beimplemented as a hardware circuit comprising custom VLSI circuits orgate arrays, off-the-shelf semiconductors such as logic chips,transistors, or other discrete components. A system or unit may also beimplemented in programmable hardware devices such as field programmablegate arrays, programmable array logic, programmable logic devices or thelike. A system or unit may also be implemented in software for executionby various types of processors. A system or unit or component ofexecutable code may, for instance, comprise one or more physical orlogical blocks of computer instructions which may, for instance, beorganized as an object, procedure, or function. Nevertheless, theexecutables of an identified system or unit need not be physicallylocated together, but may comprise disparate instructions stored indifferent locations which, when joined logically together, comprise thesystem or unit and achieve the stated purpose for the system or unit.

Further, a system or unit of executable code could be a singleinstruction, or many instructions, and may even be distributed overseveral different code segments, among different programs, and acrossseveral memory devices. Similarly, operational data may be identifiedand illustrated herein within modules, and may be embodied in anysuitable form and organized within any suitable type of data structure.The operational data may be collected as a single data set, or may bedistributed over different locations including over different storagedevices and disparate memory devices.

Furthermore, as will be described herein, systems/units may also beimplemented as a combination of software and one or more hardwaredevices. For instance, controller may be embodied in the combination ofa software executable code stored on a memory medium (e.g., memorystorage device). In a further example, a system or unit may be thecombination of a processor that operates on a set of operational data.

As noted above, some of the embodiments may be embodied in hardware. Thehardware may be referenced as a hardware element. In general, a hardwareelement may refer to any hardware structures arranged to perform certainoperations. In one embodiment, for example, the hardware elements mayinclude any analog or digital electrical or electronic elementsfabricated on a substrate. The fabrication may be performed usingsilicon-based integrated circuit (IC) techniques, such as complementarymetal oxide semiconductor (CMOS), bipolar, and bipolar CMOS (BiCMOS)techniques, for example. Examples of hardware elements may includeprocessors, microprocessors, circuits, circuit elements (e.g.,transistors, resistors, capacitors, inductors, and so forth), integratedcircuits, application specific integrated circuits (ASIC), programmablelogic devices (PLD), digital signal processors (DSP), field programmablegate array (FPGA), logic gates, registers, semiconductor devices, chips,microchips, chip sets, and so forth. However, the embodiments are notlimited in this context.

Also noted above, some embodiments may be embodied in software. Thesoftware may be referenced as a software element. In general, a softwareelement may refer to any software structures arranged to perform certainoperations. In one embodiment, for example, the software elements mayinclude program instructions and/or data adapted for execution by ahardware element, such as a processor. Program instructions may includean organized list of commands comprising words, values, or symbolsarranged in a predetermined syntax that, when executed, may cause aprocessor to perform a corresponding set of operations.

For example, an implementation of exemplary computer system 102 (FIG. 1) may be stored on or transmitted across some form of computer-readablestorage medium. Computer-readable storage medium can be media that canbe accessed by a computer. “Computer-readable storage medium” includesvolatile and non-volatile, removable and non-removable computer storablemedia implemented in any method or technology for storage of informationsuch as computer readable instructions, data structures, programmodules, or other data. Computer storage device includes, but is notlimited to, RAM, ROM, EEPROM, flash memory or other memory technology,CD-ROM, digital versatile disks (DVD) or other optical storage, magneticcassettes, magnetic tape, magnetic disk storage or other magneticstorage devices, or any other medium which can be used to store thedesired information and which can be accessed by a computer.“Communication medium” typically embodies computer readableinstructions, data structures, and program modules. Communication mediaalso includes any information delivery media.

It is apparent that there has been provided an approach forhigh-efficiency data center cooling. While the invention has beenparticularly shown and described in conjunction with exemplaryembodiments, it will be appreciated that variations and modificationswill occur to those skilled in the art. Therefore, it is to beunderstood that the appended claims are intended to cover all suchmodifications and changes that fall within the true spirit of theinvention.

What is claimed is:
 1. A controller comprising: a memory mediumcomprising instructions; a bus coupled to the memory medium; and aprocessor coupled to the memory medium via the bus that when executingthe instructions causes the controller to: analyze an environmentalcondition of a data center; activate a heat exchanger that is directlyphysically attached to a first liquid loop and not directly physicallyattached to a second liquid loop and that provides outside air freecooling in response to the environmental condition to maintain apredetermined set point for the first liquid loop of a first coolingsystem, the first cooling system including a first pump, in the casethat an outside wet-bulb temperature surrounding the data center isbelow a free cooling set point; activate a chiller of a second coolingsystem, the chiller being directly physically attached to a secondliquid loop and not directly physically attached to the first liquidloop, the second cooling system including a second pump, operable tomaintain a pre-determined set point of the second liquid loop that islower than the set point for the first liquid loop to address theenvironmental condition in the case that the outside ambient temperaturesurrounding the data center is above the free cooling set point;operate, in response to an activation of the chiller of the secondcooling system, a flow control device that is switched to allow a lowertemperature flow from the second liquid loop into the first liquid loopthat mixes fluid from a second flow cooled by the chiller of the secondcooling system that is generated by the second pump with fluid from afirst flow that is generated by the first pump in the first liquid loopimmediately before an entry into the data center to maintain thepredetermined set point for the first liquid loop, wherein there is noflow between the second liquid loop and the first liquid loop when theflow control device has been switched to not allow flow; and activate achiller of the first cooling system to address the environmentalcondition in the case that the activation of the chiller of the secondcooling system is unable to maintain the predetermined set point for thefirst liquid loop.
 2. The controller according to claim 1, wherein theinstructions, when executed, further cause the controller to activatethe heat exchanger in response to the environmental condition tomaintain a predetermined set point for the second liquid loop of thesecond cooling system in the case that the outside ambient temperaturesurrounding the data center is below the free cooling set point.
 3. Thecontroller according to claim 2, wherein the instructions, whenexecuted, further cause the controller to: activate the chiller of thesecond cooling system to address the environmental condition in the casethat the free cooling heat exchanger is unable to maintain thepredetermined set point for the second cooling system; and operate theflow control device to maintain the predetermined set point for thesecond liquid loop.
 4. The controller according to claim 1, wherein theinstructions, when executed, further cause the controller to intermixthe first liquid loop and the second liquid loop using the flow controldevice in the case that the heat exchanger is unable to maintain thepredetermined set point for the first liquid loop of the first coolingsystem such that the flow is from the data center to the first pump,from the first pump to the flow control device, from the flow controldevice to the second pump, and from the second pump to the data center.5. The controller according to claim 1, wherein the instructions, whenexecuted, further cause the controller to activate the chiller of thefirst cooling system to: determine whether combined operation of thesecond cooling system and the heat exchanger is able to maintain thepredetermined set point for the first cooling system; and activate thechiller of the first cooling system in the case that the combinedoperation of the second cooling system and the heat exchanger is unableto maintain the predetermined set point for the first cooling system. 6.The controller according to claim 1, wherein the instructions, whenexecuted, further cause the controller to operate the chiller of thesecond cooling system to control humidity in the data center in responseto dew point control in an HVAC unit coupled to the second coolingsystem.
 7. The controller according to claim 1, wherein theinstructions, when executed, further cause a communication that istwo-way to be performed between the controller and a set of sensors thatcapture data representing attributes of an environment surrounding andwithin the data center that is used to analyze the environmentalcondition of the data center.
 8. The controller according to claim 1,wherein the second liquid loop includes a set of thermal energy storageunits.